OBJECTIVE: The study assessed factors associated over time with high use of emergency departments by patients in Quebec who had schizophrenia and a co-occurring substance use disorder.METHODS: The cohort study included 2,921 patients who received a diagnosis of schizophrenia in 2006 and had at least one emergency department visit during fiscal year 2006-2007. Generalized estimating equations were used to estimate predictors of high use of emergency departments over time.RESULTS: After adjustment for all covariates, predictors of high use over time were as follows: living in either a university medical region (OR=2.10) or a peripheral medical region (OR=2.10), frequent hospitalization (OR=1.16), and greater number of psychiatric (OR=1.64) or physical comorbidities (OR=1.23).CONCLUSIONS: Because high use of emergency departments is a strong indicator of poor care continuity, identified associated factors could help develop and offer new programs to be deployed in the community to better support these patients with greater needs.